Proteins destined for the plasma membrane, secretion, or other cellular compartments are synthesized and assembled in the endoplasmic reticulum (ER). Their integrity and subsequent passage through the secretory pathway is regulated by a quality control system composed of resident ER proteins (chaperones, foldases, etc.) capable of sensing a polypepetide's state of foldedness. I am interested in understanding how these ER proteins work together to process polypeptides as they are made and how they carry out quality control functions. Recently, evidence has been given for the existence of a "matrix" of weakly-associated chaperone proteins. It has been postulated that this matrix, in addition to preventing inappropriate aggregation of newly synthesized proteins, might function like a "mixed-bed affinity chromatographic column" in the sorting of folded from unfolded proteins. Such a matrix would be expected to have profound effects on the mobility of proteins in the ER. Thus, quantifying protein mobility in the ER as a function of these variables could yield important insight into the organization and behavior of the protein folding machinery in vivo. Using state-of-the-art laser-based fluorescence microscopic techniques, I am developing methods to measure protein-protein interactions as a function of protein mobility, in the endoplasmic reticulum of living cells. Chaperones fusion proteins with the green fluorescent protein will be designed for these experiments. The resources at the Computer Graphics Laboratory have been and will be important for my project in the following ways 1) computer-based assistance in the molecular biological design aspects of my proteins under study; and 2) computer facilities to develop analysis protocols to deconvolve the fluorescence microscopic data acquired.